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Dr. S. Nishan Silva (MBBS)

The Skeletal System. Dr. S. Nishan Silva (MBBS). Under the Skeletal System. Function Classification Histology Formation Gross Anatomy. Function of the Skeletal System. Support- framework that supports body and cradles its soft organs Protection- for delicate organs, heart, lungs, brain

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Dr. S. Nishan Silva (MBBS)

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  1. The Skeletal System Dr. S. Nishan Silva (MBBS)

  2. Under the Skeletal System • Function • Classification • Histology • Formation • Gross Anatomy

  3. Function of the Skeletal System • Support- framework that supports body and cradles its soft organs • Protection- for delicate organs, heart, lungs, brain • Movement- bones act as levers for muscles • Mineral storage- calcium & phosphate • Blood cell formation- hematopoiesis

  4. Functions: Support The bones of the legs, pelvic girdle, and vertebral column support the weight of the erect body. The mandible (jawbone) supports the teeth. Other bones support various organs and tissues.

  5. 2.Protection The bones of the skull protect the brain. Ribs and sternum (breastbone) protect the lungs and heart. Vertebrae protect the spinal cord Movement Skeletal muscles use the bones as levers to move the body.

  6. Reservoir for minerals and adipose tissue 99% of the body’s calcium is stored in bone. 85% of the body’s phosphorous is stored in bone. Adipose tissue is found in the marrow of certain bones Hematopoiesis Blood cell formation. All blood cells are made in the marrow of certain bones

  7. Types of Bones • Long Bones- metacarples, metatarsals, phelangies, humerus, ulna, radius, tibia, fibula • Short Bones- carpals, tarsals • Flat Bones- rib, scapula, skull, sternum • Irregular Bones- vertebrae, some facial bones • Sesamoid- patella

  8. CLASSIFICATION of BONES 1.long bones = length is greater than breadth = consists of shaft (diaphysis) & two extremities (epiphysis) diaphysis = filled with yellow marrow = cylindrical, large space or canal at the center = periosteum epiphysis = made up of cancellous tissue e.g.: femur, humerus, tibia, fibula, radius, ulna, phalanges Membranes: 1. periosteum 2. endosteum

  9. Bone Classification Long Bones Much longer than they are wide. All bones of the limbs except for the patella (kneecap), and the bones of the wrist and ankle. Consists of a shaft plus 2 expanded ends. Your finger bones are long bones even though they’re very short

  10. CLASSIFICATION of BONES cont’n. 2. short bones = cuboidal in shape = spongy bone with thin coat of compact bone = sesamoid bone -- short bone embedded in a tendon e.g.: patella e.g.: carpals (wrist), tarsal (ankle) bones 3. flat bones = broad or elongated flat plates = for protection & muscle attachments composition: 2 thin layers of compact tse. enclosing a thin layer of spongy bone e.g.: bones of the skull, sternum, ribs, scapula

  11. 2. Short Bones Roughly cube shaped. Bones of the wrist and the ankle.

  12. Flat Bones Thin, flattened, and usually a bit curved. Scapulae, sternum, (shoulder blades), ribs and most bones of the skull. Sternum

  13. CLASSIFICATION of BONES cont’n. 4. Irregular bones = all other bones not assigned to the previous groups e.g.: vertebrae pelvic bones bones of the base of the skull

  14. 4. Irregular Bones Have weird shapes that fit none of the 3 previous classes. Vertebrae, hip bones, 2 skull bones ( sphenoid and the ethmoid bones). Sphenoid Bone

  15. Bone Classification

  16. Bone 65% mineral 35% organic Calcium Phosphste Hydroxy-apatite 90% Type 1 Collagen 10% Other matrix proteins Lipids Phospholipids Proteoglycants etc

  17. Bone Cells • Osteoblasts • Synthesize matrix; type 1 collagen • Osteocytes • Control extra-cellular calcium and phosphorus • Osteoclasts • Synthesize acid phosphatase and hydrogen ions • Remove bone minerals and matrix

  18. Bone Cells Bone tissue is a type of connective tissue, so it must consist of cells plus a significant amount of extracellular matrix. Bone cells: Osteoblasts Bone-building cells. Synthesize and secrete collagen fibers and other organic components of bone matrix. Initiate the process of calcification. Found in both the periosteum and the endosteum

  19. The blue arrows indicate the osteoblasts. The yellow arrows indicate the bone matrix they’ve just secreted.

  20. 2. Osteocytes Mature bone cells. Osteoblasts that have become trapped by the secretion of matrix. No longer secrete matrix. Responsible for maintaining the bone tissue. The osteocyte is “trapped” within the pink matrix

  21. 3.Osteoclasts Huge cells derived from the fusion of as many as 50 monocytes (a type of white blood cell). Cells that digest bone matrix – this process is called bone resorption and is part of normal bone growth, development, maintenance, and repair. Concentrated in the endosteum.

  22. Bone Matrix: Consists of organic and inorganic components. Organic component consists of several materials that are secreted by the osteoblasts: Collagen fibers and other organic materials These (particularly the collagen) provide the bone with resilience and the ability to resist stretching and twisting

  23. Inorganic component of bone matrix Consists mainly of 2 salts: calcium phosphate and calcium hydroxide. Bone also contains smaller amounts of magnesium, fluoride, and sodium. These minerals give bone its characteristic hardness and the ability to resist compression.

  24. Anatomy of a Long Bone spongy bone Proximal epiphysis compact bone Endosteum diaphysis epiphyseal line yellow marrow Sharpey’s fibers Distal epiphysis periosteum hyaline cartilage

  25. 2 Types of Bone Compact bone Spongy bone

  26. CLASSIFICATION of BONES • According to structure 1. compact = solid mass; dense & hard = forms the outer layer of bone structure = functional unit --- Haversian system 2. cancellous or spongy = contain spaces filled with bone marrow = incomplete Haversian system

  27. Long Bone Structure Shaft plus 2 expanded ends. Shaft is known as the diaphysis. Consists of a thick collar of compact bone surrounding a central marrow cavity In adults, the marrow cavity contains fat - yellow bone marrow

  28. Expanded ends are epiphyses Thin layer of compact bone covering an interior of spongy bone. Joint surface of each epiphysis is covered with a type of hyaline cartilage known as articular cartilage. It cushions the bone ends and reduces friction during movement.

  29. The external surface of the entire bone except for the joint surfaces of the epiphyses is covered by a double-layered membrane known as the periosteum Periosteum is richly supplied with nerve fibers, lymphatic vessels and blood vessels. These enter the bone of the shaft via a nutrient foramen.

  30. Periosteum is connected to the bone matrix via strong strands of collagen Internal bone surfaces are covered with a delicate connective tissue membrane known as the endosteum. Covers the trabeculae of spongy bone in the marrow cavities and lines the canals that pass through compact bone. Contains both osteoblasts and osteoclasts.

  31. MICROSCOPIC STRUCTURE OF COMPACT BONE

  32. Haversian System osteon osteocyte • Osteon with central haversian canal containing • Cells • Vessels • Nerves • Volkmann’s canal • Connects osteons Picture courtesy Gwen Childs, PhD. Haversian canal Volkmann’s canal

  33. Spider-shaped osteocytes occupy small cavities known as lacunae at the junctions of the lamellae. Hairlike canals called canaliculi connect the lacunae to each other and to the central canal. Canaliculi allow the osteocytes to exchange nutrients, wastes, and chemical signals to each other via intercellular connections

  34. Bones - Animation

  35. Another Classification for -Types • Lamellar bone • Normal, mature, structured • Woven bone • Weak, fragile, immature, randomly organized • Ex • Bones in newborns • Fracture repair callus • Bone tumors

  36. CLASSIFICATION of BONES cont’n. • According to location A X I A L skull 22 hyoid 1 ossicles 6 vertebrae 26 ribs & sternum 25_ 80

  37. CLASSIFICATION of BONES cont’n. • According to location APPENDICULAR Upper ExtremitiesLower Extremities clavicle 2 hip bone 2 scapulae 2 femur 2 humerus 2 patella 2 radius 2 tibia 2 ulna 2 fibula 2 carpals 16 tarsals 14 metacarpals 10 metatarsals 10 phalanges 28__ phalanges 28__ 64 62

  38. Table. 6.2

  39. GROSS ANATOMY OF A LONG BONE

  40. Blood Supply • Long bones have three blood supplies • Nutrient artery (intramedullary) • Periosteal vessels • Metaphyseal vessels Periosteal vessels Nutrient artery Metaphyseal vessels Figure adapted from Rockwood and Green, 5th Ed

  41. Nutrient Artery • Normally the major blood supply for the diaphyseal cortex (80 to 85%) • Enters the long bone via a nutrient foramen • Forms medullary arteries up and down the bone

  42. Periosteal Vessels • Arise from the capillary-rich periosteum • Supply outer 15 to 20% of cortex normally • Capable of supplying a much greater proportion of the cortex in the event of injury to the medullary blood supply

  43. Metaphyseal Vessels • Arise from periarticular vessels • Penetrate the thin cortex in the metaphyseal region and anastomose with the medullary blood supply

  44. Bone Marrow soft tissue occupying the medullary cavity of a long bone, the spaces amid the trabeculae of spongy bone, and the larger haversian canals. There are 2 main types: red & yellow. Red bone marrow = blood cell forming tissue = hematopoietic tissue

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